OBJECTIVES: The objectives of this research proposal are to determine the mechanism underlying the phenomenon of plasma renin activation and to characterize by physical and chemical methods the nature of circulating renin in blood. It has been proposed that renin activation occurs via a "prorenin" convertase system which activates either renin or another renin-like enzyme in blood. Isolation and characterization of this activated enzyme and a comparison with the physical chemical parameters of circulating plasma renin will establish the nature of this enzyme. The parameters to be measured include molecular weight, isoelectric point, electrophoretic mobility and kinetic rate constants. The components of "prorenin" convertase system will also be isolated and characterized to determine the mechanism of renin activation.